Patent Literature 1 discloses an X-ray detector. The X-ray detector includes a photoelectric conversion substrate, a fluorescence conversion film formed on a surface of the photoelectric conversion substrate and a light reflecting layer formed on the photoelectric conversion substrate and the fluorescence conversion film. The fluorescence conversion film is formed with a columnar crystal structure in which a plurality of columnar crystals are formed in an in-plane direction of the photoelectric conversion substrate. The light reflecting layer seals the fluorescence conversion film by causing a peripheral portion thereof to adhere to the photoelectric conversion substrate. The light reflecting layer is formed of a mixture of an adhesive material having fluidity and a powder of an inorganic material having a higher refraction index than the adhesive material.